Ship That Changed the World

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Ship That Changed the World

PBS Airdate: June 2, 2021

NARRATOR: In icy Nordic waters, a mysterious wreck…

BRENDAN FOLEY (Underwater Archaeologist): There’s nothing else like it. We’ve never seen anything else like this, archeologically.

NARRATOR: …the long-lost warship of a late medieval king…

JON ADAMS (Underwater Archaeologist): It’s a statement of power; it’s floating propaganda.

NARRATOR: …sunk under mysterious circumstances over 500 years ago; what secrets does it hold?

How did it come to be here? What cargo did it contain?

NIKLAS ERIKSSON (Archaeologist): And we were jumping up and down and said, “We have found a figurehead.”

BRENDAN FOLEY: That’s great, unbelievable.

PHIL SHORT (Dive Safety Officer): Yeah, it’s amazing.

NARRATOR: Written records of the time described it as a fearsome vessel…

BRENDAN FOLEY: It was designed to project power. It was a floating castle.

NARRATOR: …more powerful than the Viking ships that preceded it. How was it built to be so large?

JON ADAMS: We’ve got some things we don’t understand, frankly.

NARRATOR: And could it have been part of the technological revolution that built the great ships of exploration that carried Columbus and others across the Atlantic and around the world?

BRENDAN FOLEY: Designed for the same types of mission, built in the same way, this is our look at what Columbus and his crew actually experienced on their voyages of exploration.

FILIPE CASTRO (Underwater Archaeologist): That’s what makes this shipwreck so important. It’s a treasure, in fact.

NARRATOR: There’s only one way to find out…

BRENDAN FOLEY: Excavation time…

NARRATOR: …if it’s the Ship That Changed the World, right now, on NOVA.

Stora Ekön, a small island off the coast of Sweden: marine archaeologists Brendan Foley…

BRENDAN FOLEY: Excavation time…

NARRATOR: …and Johan Rönnby, along with a team of divers, have come here to investigate the crumbling timbers of a ship.

It may not look like much, but they suspect it may be a rare type of warship. Large portions of the wreck appear to still be intact.

PHIL SHORT: I can see a ship! I can see the bow, the stern, the ribs. I can see a ship.

NARRATOR: Visible in the sediment, several tell-tale items…

BRENDAN FOLEY: They’re artifacts emerging; saw a nice lead cannonball.

NARRATOR: ...and an oddly carved piece of wood, possibly the remnant of a gun carriage, built to hold an early type of cannon. Its distinctive design suggests that this object dates back to the late medieval era, 500 years ago, a time of castles and armored knights and the first stirrings of the European renaissance.

JOHAN RӦNNBY (Underwater Archaeologist): It’s the period of Michelangelo or Leonardo Da Vinci. It’s this period in European history where a lot of things are changing.

NARRATOR: And yet, ironically, this ship may have been hiding in plain sight since the 1970s, when amateur divers first stumbled across it, without realizing what they’d found.

CHRISTER FŌRBERG (Local Diver): Fisherman had told that every time I was fishing at this place, they got stuck with the equipment. And they say we go down here and look. And Neesa go down, and when he come up he said to me, “I don’t know. Must be a wreck.”

NARRATOR: That, in and of itself, wasn’t unusual. Shipwrecks are common in these waters. And then, archaeologist Niklas Eriksson found a strange artifact, and the wreck started to make headlines.

NIKLAS ERIKSSON: So, I was swimming back and forth and having a look at the loose timbers that are lyingscattered around there. I found a thick beam. After removing some sediments, we came back to the surface and we were jumping up and down and said, “We have found a figurehead. Was quite amazing.”

NARRATOR: Centuries ago, this bizarre, intricately carved figurehead would have been one of the ship’s key identifying features. It’s clearly some kind of monster, similar to the fantastical creatures that often adorned old Viking ships; in its jaws, a screaming man.

JOHAN RӦNNBY: I think you can see it as part of the psychological warfare really, because this is the first thing you meet when it is coming.

BRENDAN FOLEY: As propaganda goes, this is pretty powerful stuff.

NARRATOR: But the figurehead alone was not enough to make a positive I.D. Military historian Ingvar Sjöblom soon put the clues together.

INGVAR SJÖBLOM (Military Historian): It was probably a very rich man that could have the money to build a large ship of this size.

NARRATOR: Along with other clues gleaned from the wreckage, the figurehead and gun carriages suggest that this could be the flagship of a Danish king named Hans. Over 500 years ago, the monarch was famous for building a large naval fleet, led by a massive warship known as the “Gribshunden,” the Griffen Dog.

BRENDAN FOLEY: It’s the capital ship of King Hans. It’s the aircraft carrier; it’s the ballistic missile submarine.

JON ADAMS: It’s a statement of power; it’s floating propaganda.

BRENDAN FOLEY: Now I really understand what’s down there.

NARRATOR: Four chronicles mention Gribshunden by name, as does a single eyewitness account, written by a young nobleman who survived the ship’s sinking. They report that, in 1495, the Griffen Dog came to this island, seeking shelter, before sinking under strange circumstances.

BRENDAN FOLEY: The finds yesterday were really exciting, quite spectacular. And I think we’re going to have the same today.

NARRATOR: Now, Foley and Rönnby are preparing to uncover this ship’s secrets. The work won’t be easy. Though the wreck is not in deep water, it is mostly covered in heavy sediment. Excavating requires a highly skilled support team and extreme caution.

PHIL SHORT: You’ll be told who is the dive leader for that rotation, and their word is god.

NARRATOR: To keep them safe as they work, dive safety officer Phil Short and his crew will monitor the divers at all times.

PHIL SHORT: It is a shallow site, but you can’t breathe water at nine meters or 90, so safety is absolutely paramount.

NARRATOR: Their base of operations is a 30-foot dive boat, hauling up to 10 divers and their gear.

PHIL SHORT: We can jump in the water and get to work. And you can take samples.

NARRATOR: A temporary lab, back on shore, is set up to process any artifacts they recover.

Their time is limited. They only have the dive boat and this team together for 16 days. Their first objective is to understand how much of the ship is still intact beneath the sediment.

JOHAN RӦNNBY: We have to excavate further down, so we have to remove the silt around it, so you get the whole structure of it.

NARRATOR: The first step is to expose the cargo hold all the way down to the hull, itself a critical clue. Only once the sediment is stripped away will they get a sense of what kind of ship this was and what it was carrying.

But before they remove a single handful of sediment, the archaeologists need to create a virtual copy of the undisturbed wreck. Each day, a pair of photographers films and photographs the site. High definition video offers a detailed visual record of the archaeological work, while a second camera records thousands of stills.

BRETT SEYMOUR (Underwater Photographer, United States National Park Service): So, basically, what I’m doing is I physically have a camera, an underwater camera, and I’m just swimming back and forth in a rather systematic way, back and forth, on the site.

NARRATOR: The roughly 4,000 images are then run through a program that stitches them together, producing a 3D model, in a process called “photogrammetry.”

BRETT SEYMOUR: And then, the last step is we, basically, take and we lay the photographs on top to give it a photorealistic view.

NARRATOR: Each day, fresh images of the site will be captured, allowing archaeologists to digitally retrace their steps even after excavation is complete.

BRETT SEYMOUR: So, we’ll see where things came from in the 3D space.

RODRIGO PACHECO-RUIZ (Maritime Archaeologist): And I think that’s the really, really interesting thing about these techniques is that we can see this every day, which is fantastic. You can see the progress.

NARRATOR: Mapping expert Paola Derudas, can use this first model to create an even more detailed version. Yet even now, they can clearly see the first major obstacle: piles of loose decking blocking their access to the lower levels of the ship.

JON ADAMS: A complete ship would be easy to understand for what it is. But if you imagine the top half to two-thirds of that ship, essentially taken apart and collapsed in on itself, what you’ve got then is the seabed scattered with timbers lying all directions, and it looks very confusing.

NARRATOR: Like a game of pick-up-sticks, each timber must be moved out of the way without shifting or damaging the rest of the wreck.

BRENDAN FOLEY: It has to be very carefully controlled, because sooner or later we’re going to come across an area where there are particularly valuable things.

JON ADAMS: Marine deposit like this, it’s not compact. It’s soft. The challenge is to actually excavate that with enough precision to not damage anything, not lose anything, and derive as much of the archeological information as possible.

NARRATOR: So, the team installs scaffolding…

JON ADAMS: We’ll move it into the wreck, so it ends up here.

NARRATOR: …not only to minimize damage to the site, but to map the location of artifacts and other features.

BRENDAN FOLEY: We’re all set up, and we’re ready to roll. We’re going to excavate. It’s what we’re here to do.

NARRATOR: But as soon as they set out, they run into a problem. The conditions are terrible.

JON ADAMS: It’s really easy to stir up sediment.

PHIL SHORT: That destroyed the visibility to, virtually, zero.

NARRATOR: Their only option: to use a hand-held dredge, essentially an underwater vacuum, to try to direct the powdery sediment away from the site.

JON ADAMS: Dredge is working beautifully. The visibility’s fantastic.

NARRATOR: And then finally, they spot something significant in the clearing mud.

RODRIGO PACHECO-RUIZ: Chain mail. It’s really, really fragile. And it’s within leather, as well. It is all clumped together. They’re all rings. It could be the end of a sleeve, and then they could be connected to mail of iron.

NARRATOR: Incredibly, it’s a fragment of medieval chainmail, possibly worn by a soldier, or even a medieval knight.

RODRIGO PACHECO-RUIZ: That bit is un-corroded.

NARRATOR: It’s an astonishingly lucky find. Seawater is brutally corrosive to metals.

ROLF WARMING (Society for Combat Archaeology): Usually, aboard ships, you have heavy infantry. And at this time, it was typical for the heavy infantry to wear plate armor and also some mail, which is great protection against swords and other sorts of weaponry.

NARRATOR: Not far away, additional evidence of warfare…

BRENDAN FOLEY: And you saw the lead shot from the gun, cannonball.

EVAN: That was fantastic.

NARRATOR: …cannonballs and more gun carriages.

INGVAR SJÖBLOM: We have found nine gun carriages that is salvaged. We know that it’s others down in the wreck.

NARRATOR: The weapons themselves are gone, salvaged or rusted away, but the carriages offer some insight.

BRENDAN FOLEY: The wrought iron guns are really the predecessors to cannons. So, they’ve only got a bore of maybe three inches, but that’s a big gun for the time.

NARRATOR: They are some of the earliest cannon-like weapons to be adapted for naval warfare, yet the records are unclear if they were ever used in combat.

Only five historical sources describe Gribshunden, with few details. Instead, most of the focus is on King Hans himself.

LOVISA BRÄNNSTEDT (Historian): When we look at the written sources, they describe King Hans as witty, as wealthy, as, kind of, a happy-go-lucky man. They even describe his good looks.

NARRATOR: Hans, like other European rulers at the time, was fighting to establish his supremacy.

JOHAN RӦNNBY: These guys really needed to show that they’re powerful kings, and having a big ship, a big flagship, with a lot of flags and paint and so on, is a way to show that you’re something special.

LOVISA BRÄNNSTEDT: I think this is one of the reasons why King Hans is so keen to have this kind of ship, to really demonstrate his power.

NARRATOR: Records show that Hans took his massive new warship on diplomatic voyages to Norway, down to England, perhaps even farther, to Nordic colonies in the west.

LOVISA BRÄNNSTEDT: We have to imagine the ship as a novelty, something perhaps hereto unseen in the Nordic countries. And the fact that King Hans uses this ship, this is something he’d do in order to make a political statement.

NARRATOR: In 1495, records show, Hans outfitted his warship for yet another expedition, this time to Sweden, when an unexpected storm forced him to take shelter near the island of Stora Ekön.

JOHAN RӦNNBY: Which must have been a very good place to anchor, because it’s quite open sea outside of the island, but if you go around it on the inside, it’s quite sheltered. It’s a good anchor place.

NARRATOR: The records disagree on what happened next, but based on the artifacts the team is now finding, it appears Hans was prepared for a fight. Weaponry continues to emerge, this time, a crossbow.

JON ADAMS: Crossbow…has a crossbow bolt with it.

BRENDAN FOLEY: It’s a really interesting time period, where you still have the bow and string weapons, when you’re getting the projectile weapons with gun powder.

NARRATOR: Though the Gribshunden did have larger guns, records are unclear whether handheld firearms were used. Instead, King Hans likely relied on crossbows.

ROLF WARMING: We know, from 1507, that King Hans, he stipulates that half of the crewmembers, or half of the soldiers, they would be equipped with crossbows and the other half with lances.

NARRATOR: Though not as advanced as gunpowder weapons, they were no less dangerous in the right hands, more than strong enough to penetrate an enemy soldier’s armor.

LENA EKLUND (World Champion Crossbow Archer): It’s absolutely deadly. Chain mail, absolutely, this can go through. I’ve tested it.

BRENDAN FOLEY: Hello, Lena. I’m Brendan.

LENA EKLUND: Hi. Nice meeting you.

NARRATOR: Lena Eklund is a world champion crossbow shooter, beating both her female and male competitors.

LENA EKLUND: In the rules it says that you have to name the best woman, because they think women won’t win. But, last year I did win, so they had to name the best man.

NARRATOR: Foley has brought her a 3D print of the crossbow stock recently found onboard the Gribshunden.

BRENDAN FOLEY: So, I’m really curious to compare it against your working…

LENA EKLUND: Yeah, of course. This is my stock. You’d have had to have a stronger bow on that, I think, than I have on mine.

MARKUS: But how, how effective would that be?

LENA EKLUND: You could absolutely shoot through chain mail and maybe through armor, too.

NARRATOR: However, crossbows couldn’t be reloaded quickly. On land, that meant taking cover behind fortifications, like castle walls, while at sea, medieval drawings show they relied on “floating castles.” It’s possible the planks the team found scattered on the surface of the wreck are remnants of such a defense.

BENJAMIN ASMUSSEN (Maritime Museum of Denmark): I think this crossbow helps establish the idea of this ship as, basically, a floating castle.

BRENDAN FOLEY: That term forecastle, goes back to ships like Gribshunden that, quite literally, were floating castles. They had ramparts, sort of, built up at the forward end and at the aft end: sterncastle, forecastle.

NARRATOR: These castles were a critical element, not only for protecting crossbowmen and soldiers, but for attacking, as well.

JON ADAMS: One tactic was to try and get your forecastle, which was a big powerful structure on the bow of the ship, if you could get that over the waist of the other ship, that would give you an advantage. You could shoot down on decks. They were literally, I mean, we use the term “floating castles,” they were.

NARRATOR: And then, they find something truly unexpected.

JON ADAMS: Looks like a handgun, the metal doesn’t survive, because iron degrades in this sort of chemical environment under water, but the wood survives very well. That’s fantastic that it’s in such complete condition.

NARRATOR: It is an arquebus, one of the very earliest handheld firearms.

BRENDAN FOLEY: Oh, let me tell you how excited I am about that gun, very excited.

ROLF WARMING: This is possibly the oldest handgun found on a shipwreck, so it’s absolutely unique.

NARRATOR: It appears King Hans was surrounded by the most advanced weaponry of the medieval era.

BRENDAN FOLEY: What Gribshunden has proven to be is a combined arms platform. We’ve got medieval weapons, like a crossbow, even older weapons, like pikes and stabbing weapons, but we’ve also got this new thing, these gunpowder weapons, and that’s really something.

NARRATOR: And yet, the team is starting to suspect that the most powerful weapon in King Hans’ arsenal may have actually been Gribshunden herself.

As they dig deeper into the wreck, Rönnby and Foley suspect that this ship may have been one of the most advanced vessels of her time.

The final proof will be in the hull. How was it constructed? If this is the Griffen, can it reveal anything about the transition from earlier ships, like the smaller, Viking-style craft to the super-sized, long-distance vessels that would come to dominate European fleets?

Previously, European ships were built largely using traditional designs handed down for generations. In northern Europe, where Gribshunden sank, that meant building ships much the same way that the Vikings had built their fearsome longboats. One of the most distinctive features of these ships were their hulls.

JON ADAMS: You can’t mistake it. You’ll see the strakes, a line of planks running from bow to stern. And you can see the ribbed appearance, the sort of lapped appearance.

NARRATOR: A boat’s hull is essentially a shell built around an interior that is lighter than water, which keeps it afloat. For thousands of years, northern shipwrights built their shells in a very distinctive way.

JOHAN RӦNNBY: This is a long, long tradition, for almost 2,000 years, to build boats like this. And typical for that is that you have the boarding planking overlapping, like this way, and then you put a nail through the planks to keep them together.

NARRATOR: Known as “clinker” hulls, they rely on long planks of wood that are slightly overlapped and then squeezed together with rivets, to produce a sturdy, sea-worthy wooden shell.

Once the outer planks were in place, internal supports were added to give it additional strength. These ships were typically equipped with a single mast and square sail.

FILIPE CASTRO: The use of the single square sail in the north of Europe, again, goes back many centuries. It’s a technology that was very well controlled, very well known and very simple to operate.

JON ADAMS: A big square sail of the period would’ve, would’ve been better at driving with the following wind.

NARRATOR: The resulting ship is light, due to its thin planks and fasteners, sitting high in the water and reducing drag.

JON ADAMS: They were excellent sea craft. They ride with the waves, they don’t smash through them.

NARRATOR: But their design also makes them flexible.

KROUM BATCHVAROV (Underwater Archaeologist): Years ago, when they were still building the replica of the long Viking ship from Roskilde, the master shipwright, he grabbed one of the posts and shook it, and you could see the entire vessel waving all the way to the other end. It is that flexible.

NARRATOR: But this flexibility is also one the major limitations of the clinker design: as ship size increases, flexibility becomes the enemy.

FILIPE CASTRO: Boats should not be flexible. The history of shipbuilding is the history of making sturdier and less flexible hulls.

NARRATOR: With the introduction of heavy cannons, clinker ships faced serious stability and stress issues.

FILIPE CASTRO: As the stresses increase with the size of the vessel, that fasteners that you need to use to put these planks are going to become less sturdy. They start making water.

NARRATOR: Much larger than the typical Viking ship, the Gribshunden seems to have also been sturdy. In fact, as the chronicles show, King Hans used it to make multiple ocean voyages, and that is what intrigues the archeological team.

This ship must have been built using a different kind of construction. The archaeologists need to uncover the ship’s hull and interior structures to learn more.

After shifting the timbers blocking access to the lower levels of the ship, the team can now begin excavating in earnest.

JOHAN RӦNNBY: I’m actually going to excavate on the outside of the ship, take that down as deep as possible.

BRENDAN FOLEY: The excavation is going very, very quickly now. We have four highly competent excavators.

Now it’s starting to become clear. Now we can see exactly where we are in the ship.

NARRATOR: If they want to figure out exactly how unique the Gribshunden was, they need to uncover a key piece of the ship’s structure, its hull. But given their constraints, they’ll only be able to excavate within a narrow area, marked by the frame they’ve placed amid ship.

JON ADAMS: The middle of the ship, in terms of the hull design, it’s the most diagnostic place, so we wanted to get a look at the structure at that point.

JOHAN RӦNNBY: It’s always hard to know where to dig. We wanted to have quite a lot of the interior of the ship, so it’s a combination of getting too much ship construction as possible, but also get the inside of it, the cargo.

NARRATOR: And then, a new problem.

JON ADAMS: Some of it’s missing. We are missing a part over here.

NARRATOR: They are looking for the hull of the ship and where it connects to the internal structure, its skeleton. If they succeed, it could be the only hull segment of a ship of this period ever discovered. But something isn’t right.

JON ADAMS: We’d been wondering since we started. The inside of the ship meets the frames here, so this is the hull of the ship, curving up here. And we always wondered…there’s collapsed timbers all around, and we don’t understand, frankly, what had happened to the hull above this point.

NARRATOR: Looking at the wreck, they suspect that the missing section of hull was not built using the local clinker style, like the Vikings used. That wouldn’t have been sturdy enough. But there is a possible alternative for this ship’s construction, a style found hundreds of miles away, in the Mediterranean.

For thousands of years, Egyptians, Romans and others all used a similar template for their ships.

JON ADAMS: The ways of building ships go back to at least the early third millennium B.C. That’s nearly 3,000 B.C.

NARRATOR: But the Romans and their neighbors used an entirely different approach to hull construction. Could the Griffen have been built like a Roman ship?

The clue is in the planks. Unlike clinker hulls, where the planks are overlapped, the ships used by the Romans and others had planks laid flush, then locked together using dowels and joints, similar to those sometimes used in furniture.

KROUM BATCHVAROV: The planks are carved, they are each fastened to each other with mortise and tenon joinery.

JON ADAMS: And it’s been called, by some people, cabinetry rather than carpentry. But it works.

NARRATOR: Like clinker hulls, this outer shell was strengthened afterwards with internal supports. The result was a smooth-sided hull that was incredibly sturdy but labor-intensive.

FILIPE CASTRO: They would last forever, but they were very difficult to build, very expensive to build, many man-hours. So, whoever were the guys that were carving, they had to be experienced.

NARRATOR: As a result, by the medieval period, shipbuilders began changing their methods.

JON ADAMS: This technique that’s lasted for three-and-a-half- to four-thousand years, gradually starts changing. They’ve started to morph into something else.

NARRATOR: Instead of building the sturdy outer hull then adding internal frames afterwards, shipbuilders began experimenting with the reverse: starting with the internal frames first.

JON ADAMS: It doesn’t sound a particularly radical move, but, in a way, if you think about it, you’ve got to know the shape of your ship to cut the frames to put the planks on.

NARRATOR: This skeleton-first style was more technically challenging to design but allowed shipwrights to control a vessel’s shape more precisely, and thus its desired features, such as speed, size and cargo capacity…

KROUM BATCHVAROV: You’re controlling the shape of the vessel by building the frame structure first. There is geometry, there are understanding of physics that go into it.

NARRATOR: …allowing them to build larger vessels.

JON ADAMS: This is the craft of shipwrightry becoming the science of naval architecture.

NARRATOR: One type of ship to use this more robust engineering was called a “caravel,” possibly imported from the Arab world.

FILIPE CASTRO: The Arabs were amazing sailors. It’s very possible that caravels could have been invented in the northern shore of Africa.

NARRATOR: Their design made them incredibly capable.

Starting first as small fishing vessels, the caravels were soon adapted by Europeans to explore the coast of Africa, while Columbus took two of them, the Niña and the Pinta, on his first voyage to the Americas.

FILIPE CASTRO: Caravels became famous for being swift and fast. There’s an English text that says they swirl around our warships like butterflies.

NARRATOR: Could the Gribshunden be one of these advanced new caravels?

If so, it’s unlike any other known example. To begin with, the wreck of the Gribshunden is nearly 115 feet long. The largest known caravels, which might have included the Niña and Pinta, topped out at around 75.

JON ADAMS: Caravels were very good at what they did, but they’re quite small ships.

NARRATOR: Nor is it likely the Gribshunden is simply a longer version of a caravel. Building a ship is a tradeoff between size, speed and capacity. Caravels were optimized for speed, combining a sleek hull, usually, with triangular sails, called “lateen” sails.

JON ADAMS: A lateen sail gives you slightly more flexibility, in the sense that it will act more efficiently, like an airfoil, and allow the ship to sail across the wind or even a little into wind.

NARRATOR: Lateen sails are agile, but they have a drawback.

FILIPE CASTRO: There is a big problem with lateen sails, is when they get big, you need big crews.

NARRATOR: Increasing a caravel’s size thus required much larger crews. Yet the caravels, with their quick, narrow hulls, didn’t have room for the extra supplies required.

FILIPE CASTRO: The limit with caravels is size. If you do not have space to put food and water, you cannot go far away. So, you need large vessels.

NARRATOR: Based on everything the team is seeing, this wreck is clearly not a caravel. It’s a new design, something longer, wider and, as the team is now finding, carrying a huge amount of supplies.

JON ADAMS: Barrels, barrels, barrels; barrel staves, barrelheads, barrel hooping.

NARRATOR: Even after 500 years under water, the wood looks perfectly preserved. A symbol has been carved into each lid, though its meaning is unclear.

To learn more, the team takes the barrel staves back to shore, to scientist Hans Linderson. Linderson is a dendrochronologist, an expert in tree rings.

HANS LINDERSON (Dendrochronologist): We can be very accurate, but it’s very hard to do on this waterlogged oak.

NARRATOR: In addition to the barrels, Linderson’s lab also analyzes the origin of the timbers used in the ship itself. He begins by shaving the waterlogged outer wood away, revealing the preserved tree rings below.

HANS LINDERSON: We cut it like this and make the surface perfectly clear.

NARRATOR: Chalk helps the rings stand out more starkly.

HANS LINDERSON: So, we tried to do this, make it white by chalk.

NARRATOR: Then, using a microscope, he measures the width of the rings.

HANS LINDERSON: The tree ring started here, maybe in the end of May, and grew like this until the end of July or maybe the beginning of August.

NARRATOR: Each year, a tree adds another “ring” of new wood, as it grows, but some years are better than others. A drought year might produce a thinner ring; a long, wet summer might produce a thicker one.

Thus, the tree rings become a sort of fingerprint, a unique reflection of the weather in the specific time and place where this tree was growing.

HANS LINDERSON: I measure every ring. I try to get as many rings as possible, and then throw it out in our database.

NARRATOR: Linderson’s records include an estimated 50,000 reference samples, allowing him to zero in on exactly when this wood was cut: a precise ten-month window, starting in late 1482.

HANS LINDERSON: 1482 to ’83, that is the youngest tree ring we have, 1482, in this ship. Maybe after, like, August, they have cut the wood.

NARRATOR: But Linderson’s database also reveals something odd. The wood doesn’t seem to come from a Nordic country.

HANS LINDERSON: Well, in this case, we saw the sample didn’t fit to Sweden.

NARRATOR: Instead, it seems to have originated from hundreds of miles away.

HANS LINDERSON: It was close to northwest France.

NARRATOR: It’s possible this Danish warship didn’t come from a Scandinavian country at all. Its timbers are French. Even more interesting, Linderson’s analysis indicates the barrels holding the ship’s cargo come from yet another part of Europe.

HANS LINDERSON: We also determine the place where there have been growing and come from Scania, Southern Sweden and also from Poland.

BRENDAN FOLEY: Okay. That’s interesting. My colleagues tell me that Poland had a huge export market in making barrels and shipping these out all over Europe.

NARRATOR: But dendrochronology cannot reveal exactly what these barrels carried.

Fortunately, more clues are emerging from the wreck.

JOHAN RӦNNBY: I think we are in the kitchen store or something like that, because there’s so many barrels down there.

NARRATOR: In one of those barrels: bones…

BRENDAN FOLEY: And I just couldn’t see if that was wood or bone or what that was. What, what is that?

NARRATOR: …mysterious skeletal fragments. But they don’t appear to be beef bones or other common food animals.

STELLA MACHERIDIS (Osteologist, Lund University): Okay, so, Brendan, the bones that we recovered are called scutes. Based on a few of the scute fragments that you excavated, they are the remains of something at least one meter, and probably around two meters long. So, it’s quite impressive.

NARRATOR: They are bones from an Atlantic sturgeon, a massive fish, all but extinct in these waters.

STELLA MACHERIDIS: It’s kind of like bony plates that works as a shield construction on the fish. I think that this fish would have been used to be presented as a gift to the royalties. Because the sturgeon was considered one of the king’s fishes.

NARRATOR: A fish considered so valuable that, if caught, it must legally be given to royalty.

STELLA MACHERIDIS: And you would be punishable by law. And you know, you don’t want to be punished by law during the medieval, right. There’s a lot of evidence for this actually being one of the things that they would have had with them as a manifestation of power or just royal status.

NARRATOR: As they dig deeper into the cargo hold of a king, it is like a window into long-forgotten lives.

BRENDAN FOLEY: We were excavating down in the hole, amidst all those barrels, and I thought at first it was a gun, but it’s not a gun, it’s some sort of vessel. What we have here is a completely intact wooden tankard from 1495. Handle, cover, completely intact, and possibly the King’s mark on it.

The experience of excavating on a site like this is really quite visceral. Every once in a while, though, we’ll find an object that just makes us realize that we’re looking back half-a-millennium in history. And you think, “Some nobleman was the last one to hold these objects 500 years ago.” It’s the sense of, almost, time travel.

JOHAN RӦNNBY: That’s the real benefit of our archeology, traveling back in history in quite a unique way. I will say that written sources can never get you that close to history as archeology sometimes can.

NARRATOR: And then, something puzzling.

DIVER #1: It’s good stuff in there.

DIVER #2: Excellent!

DIVER #1: It’s like a leather pouch…

NARRATOR: They have found what appear to be corroded lumps of metal, wrapped in leather. It’s difficult to tell what they once were, but there may be a way to find out.

BRENDAN FOLEY: In the wreck, up close to the top of the surface of the sediment, we found what we think is a leather purse that was full of this material. So, if the machine can show us what’s in there…

DIRK: I think we can do that.

NARRATOR: The solution is a C.T. scanner, similar to that used by doctors to peer inside the human body.

DIRK: So, this just goes from the bottom up.

BRENDAN FOLEY: That’s cool, already. You can already see that there’s, there’s coins there.

NARRATOR: It’s a stack of coins.

BRENDAN FOLEY: That’s a lot, that’s a lot of coins. The question is what are they worth?

NARRATOR: It’s a small fortune, perhaps belonging to a nobleman.

It seems strange. Based on the military artifacts, it appears Gribshunden was outfitted for battle, yet she was also hauling what appears to be large amounts of food and wealth. What were King Hans and his men doing here?

To understand the odd mix of wealth and warfare, the archaeologists need to understand more about this ship, and now they are close.

KROUM BATCHVAROV: Oh, what wouldn’t I give to be able to get there.

JOHAN RӦNNBY: Yeah. This is so promising, because if we have these things here and we have... We will have the rest here, I’m quite sure about that.

KROUM BATCHVAROV: Why would it disappear?

NARRATOR: Down on the seafloor, Johan Rӧnnby is the first to see it.

BRENDAN FOLEY: It’s beautiful.

NARRATOR: They have found a remarkable piece of the ship that reveals the secret of its construction and perhaps the construction of other European great ships.

JON ADAMS: We’ve got this piece of the hull that’s collapsed outwards, but it’s done so in one lump, one coherent unit. So, in a way, it’s better than if it had stayed above the seabed, because it would all be eroding and… But now, it’s gone flat, and it’s covered up by about a meter of sediment. It’s in pristine condition.

NARRATOR: This key piece of the hull had been preserved intact, simply because it had been buried. It’s a tremendous stroke of luck.

At some point, either when the ship sank or afterwards, this entire section of hull collapsed outward.

BRENDAN FOLEY: But what we’re seeing is this piece that’s hinged down is still going under the sediment, that’s just fabulous.

JOHAN RӦNNBY: No, we are quite happy now, because the whole ship is actually there. Our excavation now really proves that.

NARRATOR: They have finally found the evidence that shows how this ship was built, from the hull, the skin of the ship, to the meticulously crafted timbers that make up the interior skeleton.

And in these timbers, the archaeological team sees the evidence of a new kind of ship, its hull built, not in the overlapping clinker style, but not purely in the style used by Mediterranean ships, like caravels, either.

JON ADAMS: So, you’ve got fastenings, you’ve got bolts, tree nails, the wooden pegs that hold everything together, and we’ve even got some, I mean, we’ve got some things we don’t understand frankly.

NARRATOR: But deciphering this incredible discovery is slow work under water.

So instead, back on shore, the team’s digital specialist, Paola Derudas, processes the photogrammetry images into a digital model.

NIKLAS ERIKSSON: Yeah, that’s quite amazing.

NARRATOR: It is a high-fidelity copy of the wreck site, offering an up-close look at their long-hoped-for discovery.

BRENDAN FOLEY: Now, we get to see the shipwreck in its entirety, for the first time.

NIKLAS ERIKSSON: When you’re down there, you can only see small part of the ship, and to have an overview like this is quite amazing.

NARRATOR: It is the earliest surviving example of the first generation of ships built in an incredible new style. As they had suspected, the construction is different from the clinker-built hulls of the Vikings and other northern ships.

NIKLAS ERIKSSON: Part of the hull, you can actually see it’s not the way that ships were built in earlier medieval period, it doesn’t look like this

NARRATOR: Nor could it be classified as a caravel, so well-known in the Mediterranean.

BRENDAN FOLEY: This one right here, Paola. If you can get…

PAOLA DERUDAS: This one?

BRENDAN FOLEY: Yeah. If you can see the cuts in it, right there.

NIKLAS ERIKSSON: Ah. This is fantastic to see one!

For the first time we can see how they were built and how much space you had inside them.

NARRATOR: Instead, it appears to be both, incorporating elements from each region into a single, unified design, a new generation of ship.

BRENDAN FOLEY: So, this is Mediterranean style; this is clinker. The dimensions are clearly different, the width and the depth.

NARRATOR: They can see in the timbers that the blueprint starts with a caravel-like hull, borrowed from the Mediterranean. But it’s wider and heavier than the sleek caravels, giving it additional capabilities.

JON ADAMS: Because its framing system is so much more robust, you could build your ship bigger and tougher, and therefore, it’s much more predisposed to carrying lots of cargo, people and weapons.

NARRATOR: Above it, lighter boards are used for the fore and aft castles, similar to the northern clinker-style hulls. The rigging appears to be also northern, featuring large square sails on two of the masts, but it adds triangular lateen sails, used by Mediterranean ships, like the caravel, added for versatility.

JON ADAMS: They arrive at this sort of technological fusion of features that makes a more versatile and seaworthy and controllable ship. It’s seakeeping qualities are good, and it needs less crew. It would’ve been as high tech as there would’ve been around at the time.

NARRATOR: It was a new kind of design that would soon change the world.

BRENDAN FOLEY: You can think about the late 15th century as a sort of space race, in the exact same way that the Americans and the Soviets and other nations were competing on a national scale to achieve a technological feat, that’s exactly what was going on in the late 15th century. All the European powers now began to develop this ship type.

NARRATOR: With Gribshunden, King Hans was one of the first to deploy one of these technologically advanced new ships. Heavily armed, he used it to intimidate. Hans was the powerful ruler of three nations: Denmark, Norway but also Sweden.

It was known as the Kalmar Union, but the union was troubled.

JOHAN RӦNNBY: It was quite a problematic relationship, because there was a lot of noblemen and powerful people, so it was a power struggle all the time. That’s really why Hans, he’s here.

NARRATOR: Records show that Hans was on his way to scare a rebellious Swedish nobleman back into line.

BRENDAN FOLEY: This was a vessel that was floating propaganda. It was really a floating castle.

JON ADAMS: When Hans turns up with his whole fleet and Gribshunden is there as one of the principal warships of his fleet, he’s making a statement.

BRENDAN FOLEY: This was raw power on display.

NARRATOR: And then, misfortune strikes.

As a storm rages out at sea, Hans anchors Gribshunden in the sheltered waters of Stora Ekön. Yet danger still lurks.

BRENDAN FOLEY: The written sources suggest that the king’s, sort of, sorcerer says that the omens are bad and the king should get off the ship, and he does.

Then the ship catches fire.

JON ADAMS: Which is partly borne out by what we’re seeing on the seabed. And we do see some of the timbers that are blackened, which are consistent with that.

BRENDAN FOLEY: And the fire reaches the powder magazine, and there’s some sort of explosion on board.

NARRATOR: It’s possible that in this way Gribshunden was a victim of her own nature, as a cutting-edge weapon of war.

BRENDAN FOLEY: Fire, today, is still probably the first or second killer of ships. Did they not yet develop the protocols to handle fire in a ship carrying gunpowder? Is that why Gribshunden was lost? It very well could be. They hadn’t yet developed the methods to keep the ship safe.

NARRATOR: It had to have been an incredible loss for King Hans, yet now the ship has become an invaluable gain for nautical history. No other vessel from this first generation of massive ships still survives.

JON ADAMS: Gribshunden I think takes us back as far as we’ve got, so far, to this period of change. Europe is changing, and ships are the tools of that change.

FILIPE CASTRO: You start having more contact. There is economic growth. Cities grow, literacy grows.

JON ADAMS: Because of population growth and economic momentum, ships of both areas start to trade in each other’s waters. So, you get this sort of technological diffusion.

BRENDAN FOLEY: We begin to get a picture of the late medieval world and all of its interconnections.

NARRATOR: And once these different regions start learning from each other, everything begins to change. Whereas King Hans sees the potential of these ships as an intimidating weapon, others see a vessel capable of pushing farther than ever before.

JON ADAMS: What you’re building is not only a ship that is tougher and bigger, you’re building it in a design which not only has capacity for cargo, but it’s got accommodation built into that architecture. This is when we start to see ships going across the Atlantic for not just days, but weeks or months at a time, or even a year or more. These are the ships of the age of global exploration.

NARRATOR: The shipbuilding advances of this period would be used by Columbus, Magellan, and those that followed, to expand Europe’s influence, laying the groundwork for empires that would transform the world, even as they enslaved peoples around the globe.

History might have played out very differently without this novel ship design, its secrets hidden in the wreck that was lost for 500 years. But now this missing chapter of history is restored to us.

Credits

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This program was produced by WGBH, which is solely responsible for its content. Some funders of NOVA also fund basic science research. Experts featured in this film may have received support from funders of this program.

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Image credit (Illustration of the Gribshunden at Sea)

© 2021 WGBH Educational Foundation

Participants

Jon Adams, Benjamin Asmussen, Kroum Batchvarov, Lovisa Brännstedt, Filipe Castro, Paola Derudas, Lena Eklund, Niklas Eriksson, Brendan Foley, Christer Førgerg, Hans Linderson, Stella Macheridis, Rodrigo Pacheco-Ruiz, Johan Rönnby, Brett Seymour, Phil Short, Ingvar Sjöblom, Rolf Warming